Mystery 'mima' mounds created by plants ?

Scientists believe that plants, not animals, are responsible for the strange vegetation-topped mounds.

Found across the American prairies and in other countries all over the world, these unexplained topographical anomalies have been the subject of scientific debate and study for years.

Several explanations have been proposed including the idea that animals such as gophers may be responsible for creating them, but now a new study has suggested that the real culprit isn't animals at all but plants - or the spatial patterning of plants to be precise.

"My sense of the literature is that people look at the mounds and think they're faunally generated by default," said study co-author Michael Cramer. "We're suggesting that people should have a more balanced view and entertain the possibility that vegetation could be behind mound formation."

Plants are not believed to generate the mounds directly but instead have a cumulative effect on the surrounding soil erosion through their growth and absorption of nutrients.

"If you have a patchwork of vegetation islands, they protect the soil from erosion, while the inter-patch soil gets eroded away," said Cramer. "This results in a deflation of the surface, which leaves behind the mounds."

It is probably a combination of erosion of the surrounding area and accretion of debris with in the mound, with the plants acting as a wind trap for sand, leaves, etc. The breakdown of organic material within the mound would act as a natural fertilizer creating over time taller plants and making the wind trap more efficient, especially towards the center of the mound. I would expect that in areas with a strong prevailing wind direction, the mounds would be elongated rather than circular.

Makes sense to me. I'm sure it would be easy to tell if it was gophers... just dig one up. I have to say that I first read the thread title as, "Mystery 'mima' sounds created by plants" and was very interested to hear a recording of plants going, "Mimmma.. mimmmaaa...."

Calls to mind how native americans farmed. They planted corn on fields of mounds and beans and squash on the ground between as additional crops and a way to retain moisture in the soil and control weeds. Native American agriculture was gardening on a grand scale.

Strange... While growing up in Northwest Arkansas I was told that instead of trenching around a tee-pee mounds were built on which to construct a tee-pee. (Would make for a awkward sleeping position being on top of a small, round hill.) However, when I was a young adult--I believe it was the Forest Service guide who told us--I was told it was a result of erosion as in natural cycles of periods like the "Dust Bowl" days. The solution to keeping your top soil after that was each state's Agriculture Dept. and groups like Arbor Day supplying people, primarily farmers, with free trees to plant alon... [More]

Native Americans didn't use plows to rip the earth open. They planted the three sisters in the east (corn, beans, squash) on mounds not unlike those in the picture, with sticks using fish heads for fertiliser. European style farming on the plains destroyed the root system of the native grasses, and when drought came there was nothing to hold the topsoil in place.